7 basic php sorting methods, 7 php sorting_PHP tutorial

7 basic php sorting methods, 7 php sorting

This article summarizes 7 commonly used sorting methods and implements them in php language.

1. Direct insertion sort

/*
 *  直接插入排序,插入排序的思想是：当前插入位置之前的元素有序，
 *  若插入当前位置的元素比有序元素最后一个元素大，则什么也不做，
 *  否则在有序序列中找到插入的位置，并插入
 */
function insertSort($arr) {
  $len = count($arr);  
  for($i = 1; $i < $len; $i++) {
    if($arr[$i-1] > $arr[i]) {
      for($j = $i - 1;$j >= 0; $j-- ) {
        $tmp = $arr[$j+1];
        if($tmp < $arr[$j]) {
          $arr[$j+1] = $arr[$j];
          $arr[$j] = $tmp;
        }else{
          break;
        }          
      }  
    }
  }  
  return $arr;
}

2. Bubble sort

/*
  冒泡排序,冒泡排序思想：进行 n-1 趟冒泡排序， 每趟两两比较调整最大值到数组（子数组）末尾
*/
function bubbleSort($arr) {
  $len = count($arr);
  for($i = 1; $i < $len; $i++) {
    for($j = 0; $j < $len-$i; $j++) {
      if($arr[$j] > $arr[$j+1]) {
        $tmp = $arr[$j+1];
        $arr[$j+1] = $arr[$j];
        $arr[$j] = $tmp;
      }
    }
  }
  return $arr;
}

3. Simple selection and sorting

/*
  简单选择排序, 简单排序思想：从数组第一个元素开始依次确定从小到大的元素
*/
function selectSort($arr) {
  $len = count($arr);
  for($i = 0; $i < $len; $i++) {
    $k = $i;
    for($j = $i+1; $j < $len; $j++) {
      if($arr[$k] > $arr[$j]) {
        $k = $j;
      }
    }
    if($k != $i) {
      $tmp = $arr[$i];
      $arr[$i] = $arr[$k];
      $arr[$k] = $tmp;
    }
  }
  return $arr;
}

4. Hill sorting

/*
  希尔排序,希尔排序原理：将数组按指定步长分隔成若干子序列，然后分别对子序列进行排序（在这是直接）
*/
function shellSort($arr) {
  $len = count($arr);
  $k = floor($len/2);
  while($k > 0) {
    for($i = 0; $i < $k; $i++) {
      for($j = $i; $j < $len, ($j + $k) < $len; $j = $j + $k) {
        if($arr[$j] > $arr[$j+$k]) {
          $tmp = $arr[$j+$k];
          $arr[$j+$k] = $arr[$j];
          $arr[$j] = $tmp;
        }
      }
    }
    $k = floor($k/2);
  }
  return $arr;
}

5. Quick sort

/*
 *  快速排序,快排思想：通过一趟排序将待排的记录分为两个独立的部分，其中一部分的记录的关键字均不大于
 *  另一部分记录的关键字，然后再分别对这两部分记录继续进行快速排序，以达到整个序列有序，具体做法需要
 *  每趟排序设置一个标准关键字和分别指向头一个记录的关键字和最后一个记录的关键字的指针。
 *  quickSort($arr, 0, count($arr) -1);
 */
function quickSort(&$arr,$low,$high) {
  if($low < $high) {
    $i = $low;
    $j = $high;
    $primary = $arr[$low];
    while($i < $j) {
      while($i < $j && $arr[$j] >= $primary) {
        $j--;
      }
      if($i < $j) {
        $arr[$i++] = $arr[$j];
      }
      while($i < $j && $arr[$i] <= $primary) {
        $i++;
      }
      if($i < $j) {
        $arr[$j--] = $arr[$i];
      }
    }
    $arr[$i] = $primary;
    quickSort($arr, $low, $i-1);
    quickSort($arr, $i+1, $high);
  }
}

6. Heap sort

/*
  堆排序
*/

// 调整子堆的为大根堆的过程，$s为子堆的根的位置，$m为堆最后一个元素位置
function heapAdjust(&$arr, $s, $m) {
  $tmp = $arr[$s];
  // 在调整为大根堆的过程中可能会影响左子堆或右子堆
  // for循环的作用是要保证子堆也是大根堆
  for($j = 2*$s + 1; $j <= $m; $j = 2*$j + 1) {
    // 找到根节点的左右孩子中的最大者，然后用这个最大者与根节点比较，
    // 若大则进行调整，否则符合大根堆的 特点跳出循环  
    if($j < $m && $arr[$j] < $arr[$j+1]) {
      $j++;
    }
    if($tmp >= $arr[$j] ) {
      break;
    }
    $arr[$s] = $arr[$j];
    $s = $j;
  }
  $arr[$s] = $tmp;
}

// 堆排序
function heapSort($arr) {
  $len = count($arr);
  // 依次从子堆开始调整堆为大根堆
  for($i = floor($len/2-1); $i >= 0; $i--) {
    heapAdjust($arr, $i, $len-1);
  }
  // 依次把根节点调换至最后一个位置，再次调整堆为大根堆，找到次最大值，
  // 依次类推得到一个有序数组
  for($n = $len-1; $n > 0; $n--) {
    $tmp = $arr[$n];
    $arr[$n] = $arr[0];
    $arr[0] = $tmp;
    heapAdjust($arr, 0, $n-1);
  }
  return $arr;
}

7. Merge sort

/*
  归并排序,这里实现的是两路归并
*/
// 分别将有序的$arr1[s..m]、$arr2[m+1..n]归并为有序的$arr2[s..n]
function Merge(&$arr1, &$arr2, $s, $m, $n) {
  for($k = $s,$i = $s, $j = $m+1; $i <= $m && $j <= $n; $k++) {
    if($arr1[$i]<$arr1[$j]) {
      $arr2[$k] = $arr1[$i++];
    }else {
      $arr2[$k] = $arr1[$j++];
    }
  }
  if($i <= $m) {
    for(; $i <= $m; $i++) {
      $arr2[$k++] = $arr1[$i];
    }
  } else if($j <= $n) {
    for(; $j <= $n; $j++) {
      $arr2[$k++] = $arr1[$j];
    }
  }
}

// 递归形式的两路归并
function MSort(&$arr1, &$arr2, $s, $t) {
  if($s == $t) {
    $arr2[$s] = $arr1[$s];
  }else {
    $m = floor(($s+$t)/2);
    $tmp_arr = array();
    MSort($arr1, $tmp_arr, $s, $m);
    MSort($arr1, $tmp_arr, $m+1, $t);
    Merge($tmp_arr, $arr2, $s, $m, $t);
  }
}

// 对一位数组$arr[0..n-1]中的元素进行两路归并
function mergeSort($arr) {
  $len = count($arr);
  MSort($arr, $arr, 0, $len-1);
  return $arr;
}

Usage experience
If the number n of records to be sorted is small, direct insertion sorting and simple selection sorting can be used. When the record itself has a large amount of information, it is better to use the simple selection sorting method.
If the records to be sorted are basically ordered by keyword, direct insertion sort and bubble sort are suitable.
If the value of n is large, quick sort, heap sort and merge sort can be used. In addition, quick sort is considered to be the best method among internal sorting methods.

The above is the entire content of this article, I hope it will be helpful to everyone’s study.

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